Alkylene oxides are typically produced via the controlled oxidation of the desired alkylene in the presence of a plurality of supported catalysts. In order to maintain a commercially acceptable selectivity, the reaction temperature is desirably varies very little, e.g., for the production of ethylene oxide the optimum reaction temperature ranges from 225° C. to 250° C. At temperatures above 250° C., the selectivity of the reaction for ethylene oxide decreases rapidly with increasing temperature. Furthermore, the reactions involved in alkylene oxide production are exothermic, particularly, the side reaction to carbon dioxide. So, heat typically must be removed from the process so that the reactions can be properly controlled.
To facilitate heat removal, shell and tube reactors, i.e., comprising a large number of tubes of a small diameter within a shell, are typically used for such reactions. Even when these reactors are used, typically with a heat transfer medium supplied between the tubes and shell, the heat given off by the reaction is so high that high space velocities of the reactants must be maintained within the tubes. Although catalyst life can be extended to some degree by increasing the operating temperature, the amount of any such increase can be limited so that a decrease in selectivity is not realized. And so, before the process becomes economically unfeasible, the spent catalyst may typically be unloaded and the reactor tubes filled with new catalyst.
However, even though intended to invigorate the process, the unloading of old catalyst and reloading with new catalyst can introduce humidity or dew into the process. This dew can cause the internal surfaces of the reactor tubes and other components comprising carbon steel to rust. The presence of rust in the reactor tubes can result in greater numbers and/or amounts of impurities being formed during the alkylene oxide process. Such impurities can be difficult to separate from the desired end-product, and can result in a sub-optimal end-product being produced.
To address the formation of rust, many processes incorporate a cleaning step in their catalyst exchange process, in which an abrasive material may be used to clean the inner surfaces of the reactor tubes and/or other reactor components. It can be difficult to remove all of any such material so used, and so, such cleaning steps may inadvertently introduce impurities into the process.
It would thus be desirable to provide improved cleaning processes for alkylene oxide reactors and/or reaction components.